Shipboard training device



F.. PIERCE EF'AL SHIPBOARD TRAINING DEVICE Feb. 5, 1957 Filed June 28,1944 3 Sheets-Sheet l NE Emma @SQEQ @9889 $58 iwg evz'iwwji $531 3 MEmink $538 986 1957 I F. PIERCE ETAL 2,780,011

SHIPBOARD TRAINING DEVICE Filed June 28, 1944 5 Sheets-Sheet 2 52 OUTPUTSHAFT 73. I l I 72 I 74 45 75 55 j; [Ill ll q 57 48 F ==-=i7a u I 4 l 16/ 69 62 /63 -67 6O 1 I 68 66 64 k p 70 AMI! 56 54 x V X 5/ m/ ur SHAFT53 F. PIERCE ET AL 2,780,011

SHIPBOARD TRAINING DEVICE Feb. 5, 1957 Filed June 28, 1944 3Sheets-Sheet 3 United States Pat SHIPBOARD TRAINING DEVICE Firth Pierceand George A. Brettell, Jr., La Jolla, Calif., assignors to the UnitedStates of America as represented by the Secretary of the NavyApplication June 28, 1944, Serial No. 542,504 5 Claims. (Cl. 3510.4)

This invention relates to a training device and more particularly to oneadapted for use in training crews of anti-submarine vessels.

Experience has shown that men are best trained when training conditionsare made to simulate as nearly as possible the actual conditions underwhich the same actions will be performed in practice. Particularly isthis true in warfare where, under the excitement and danger of action,training procedure is often forgotten.

The present invention is designed to provide training for crews of ananti-subman'ne vessel, by applying to the existing sound gear electricalsignals which produce, through the gear, audible and visual informationindicating the presence of a submarine target in the surrounding water.formation supplied by the sound gear, resembles a real target. Thesimulated target may be made to appear to move, turn, stop, etc., andengage in evasive action, and the ships crew must so conn the ship tofind, follow and destroy the simulated target. The advantage of suchtraining is that the ships stations are actually manned by the crew, allequipment is operating, and the ship is actually conned by the crew inan attempt to maneuver it into a position, with respect to the target,for an attack.

Scoring mechanisms are also provided so that instead of dropping bombsor depth charges, electric scoring switches are actuated by means ofwhich the instructor is enabled to determine whether the attack wassuccessful.

An indicating mechanism is also included on which the positions of, andrelative motion between, ship and target are shown. This is arranged tobe visible to the instructor at all times and allows him to judge theprogress of the attack at any instant.

And, additionally, controls are provided for the use of the instructorwhich enable him to adjust the course and speed of the simulated targetin a realistic manner.

Thus, the present invention, provides training for crews in obtaining,evaluating and using information made available through the ships soundgear. It accomplishes, in addition to the functions of the apparatusdisclosed in a co-pending application entitled, Attack Training Device,Serial No. 535,858, filed May 16, 1944, by Firth Pierce, George A.Brettell, Jr., Melvin O. Kappler and Clark F. Bradley, other desirableobjects. The present gear may be operated in a manner that the simulatedtarget is maneuvered in a much more realistic way; and continuouscalculations of range, range rate, bearings, etc., need not be made. Nor-is it necessary that the instructor utilize a specially designed sliderule, such as that disclosed in a co-pending application entitled, SlideRule, Serial No. 535,472, filed May 13, 1944, by Gaylord P. Harnwell, tomake such calculations. The pres ent invention does, however, make useof much of the electrical system of the device disclosed in theapplication first mentioned above, and is connected into the sound gearin substantially the same manner, so that the visual and audibleinformation from the sound gear,

A target is thus simulated which, from the in- 2,780,0ll Patented Feb.5, 1957 2 and on which the simulated is the same.

Thus, in brief, the present system comprises a mechanical arrangementfor automatically obtaining the values of and changes in speeds andbearings which may be used in conjunction with the electrical circuit ofthe application referred to above. At the outset, however, it should benoted that when the present invention is utilized, the bearing controlcircuit of that application may be eliminated.

In the drawings:

Fig. 1 is a schematic view of the mechanical arrangement of theinvention.

Fig. 2 is an electrical schematic diagram of the. contacts which controlthe echo delay time.

Fig. 3 is a detailed sectional view of one of the overtaking delaymechanisms.

Fig. 4 is a sectional view Fig. 3.

Figure 5 is an electrical schematic diagram of the circuit used inconjunction with the mechanism and circuits shown in Figures 1 through4.

The present system comprises, in general, a pair of ball componentsolvers in which the North-South and East-West components of the motionof both a ship and a simulated target are obtained. In order thatrelative motion between ship and target is available, a pair ofdifferentials is provided to obtain the differences between each of therespective components.

The output of each differential is applied separately to an indicatingmechanism comprising two pairs of rollers, each pair of which supports atransparent curtain on which is marked a hairline. The two curtains aremounted at right angles to each other and the point of intersection ofthe hairlines (with respect to a fixed point) represents the position ofthe target with respect to the ship.

Additionally, there is an electrical control system, op erating in asimilar fashion, for supplying electrical quantities proportional to thevarious values of and changes in ranges and bearings.

The arrangement of the invention is illustrated schematically in Fig. 1.Quantities representing the speed of the ship and the target areobtained from the respec tive outputs of variable speed motors 1, 2.Since the training is conducted on a ship, the speed of motor 2 isvaried to correspond to the ships actual speed in the water. The speedof motor 1, representing the speed of the target, is varied by theinstructor in a manner to represent the speed and changes in speed of anactual target.

The respective outputs of motors 1, 2 are resolved into North-South andEast-West components in a pair of ball component solvers, generallydesignated 3, 4. Each of these solvers comprises a ball 5, which isengaged by and frictionally driven through an input roller 6 by therespective speed motor. The output components are taken oif each ball 5by a pair of output rollers 7, 8, as seen in Fig. 1, to provide theNorth-South and East- West components.

The directions of motion of the target and ship are established by meansof a reversible, variable speed mo tor 9, and a conventionalgyro-compass repeater 10, respectively. The motor 9 (or gyro-compassrepeater) is utilized to drive a gear 11 which meshes with a second gear12. The latter gear is fixed to input roller 6 on the ball solver andthus determines the direction of rotation of the ball 5 and consequentlythe magnitude of each of the output components, as determined by therotation of rollers 7, 8.

attack procedure is based,

along the lines 44 of Gyro-compass repeater 10 is of conventional typeandit is obvious that the angular position of input roller 6 r tivemotion.

d is simply arranged to follow the changes in direction of the ship asevidenced by the position of the repeater. It should also be noted thatsince motor 9 simulates turning, or change in direction of thesimulated, target, its rate of turning may be made to depend upon thespeed of motor 1 in order that actual conditions, are more perfectlyrepresented, i. e., that the time required for executing a givenmaneuver is made dependent upon speed.

The difference between the North-South components of the ball solvers 3,4 is obtained by applying the outputs of output rollers 7 to adifferential 13, and the similar East-West difference component isobtained through the connection of output rollers 8 to differential '14.

The output of differential 13 is utilized to drive one of a pair ofparallel rollers 15, 15 which mount a transparent curtain 16 on which ismarked a hairline 17. The other of the pair of rollers 15 contains aprc-loaded, spring arranged in such a manner that as the first roller isdriven in one direction, the spring acts as arcstraining force tomaintain the curtain taut at all times. On the other hand, when thefirst roller is driven in the opposite direction, its driving force actssimply as a restraining force against the action of the pre-loadedspring contained in the second roller. This structure insures that thecurtain 16 is held taut regardless of the direction of drive and, at thesame time, provides means for absorbing all ofthe backlash componentsintroduced by the gearing between the ball solver 5 and the indicatingmechanism. Thus, as the rollers are rotated, the hairline 17 travels upand down, representing the North-South component of rela- In a similarway, the output of differential 14 controls a second pair of rollers 18,mounted at right angles to rollers 15. This pair of rollers alsosupports a transparent curtain 19 which carries a second hairline 20,whose motion simulates the East-West component of relative motion in thesame manner.

Underneath the transparent curtains 16, 19 is a disk 21 mounted forrotation about its central reference point 22. It carries an arrow 23,representing the direction of motion of the ship, and is directlydriven, through a gear24, by the gyro-compass repeater 1%). A fixed dial(not shown) in the form of an annulus may be mounted above the curtainson which the direction of the ship may be determined by the position ofarrow 23. Disk 21 also may be provided with a suitable bearing anddistance scale by means of which the range and bearing of theintersection of hairlines 17, 20, with respect to reference point 22 maybe determined.

It is thus seen that the indicating mechanism provides information as tothe direction of motion of the ship (arrow 23), the poistion of the ship(reference point 22), and the relative position and motion of the targetwith respect to the ship, as evidenced by the position of theintersection of hairlines 17, with respect to reference point 22.

The indicating mechanis'm described above is for the use of theinstructor in order that he may observe the procedure adopted in conningthe ship as he alters the course and speed of the target by means ofmotors 9 and 1, respectively.

Since, however, the purpose of the invention is to train sound teams inattack procedures, an electrical control mechanism is also provided toobtain, inconjunction with the existing echo-ranging gear, visual andaudible information simulatingthat which might be obtained if a realtar-get were present and was executing similar maneuvers. Intheapplication Serial N0. 535,858, filed May '16, 1944, meansaredisclosed whereby signals are applied-to existing echo-ranging equipmentto simulate a target. For the present invention, the circuit illustratedin Fig. 4 of thatapplication may well be used (with the bearing controlcircuit omitted). In place of the bearing control circuit the structureillustrated in'Fig. 1 'is'substituted.

This 'is'shown schematically in Fig. 5. The outputs of differentials.13, "14, in addition to being-applied-tothc indicating mechanism, arealso applied to a pair of rods 25, 26, respectively, mounted to roll atright angles to each other on wheels 27, 23 and racks 29, 3t),respectively. The two rods 25, 26 are slidably engaged by a block 31whose motion is determined by the motion of the rods, and whoseposition, at any time, corresponds to the position of the intersectionof hairlines 17, 20 on the indicating mechanism. Mounted below the block31 and rods 25, 26 is a non-conducting circular disk 32. This disk isprovided with a plurality of conducting inserts 33, insulated from oneanother and whose overall configuration represents the shape of thesound beam emanating from the sound projector. Disk 32 is designed to berotated by means of a gear 34 which is directly driven by the output ofa difierential 35. The inputs applied to this differential are obtainedfrom the gyro-compass repeater 1t and from a conventional repeater 36,actuated by the sound projector training mechanism, which indicates therelative bearing of the projector with respect to the ship. Thus, theoutput of differential 35 supplies orientation to disk 32 correspondingto true projector bearing. Thus, the plurality of inserts 33 maintains adirection corresponding to the direction at which the sound projector istrained.

Block 31 supports a contact 37 which slides over the surface of disk 32in a manner that, when the disk and the block 31 are properly positionedwith respect to One another, electrical contact is made between thecontact 37 and one of the contact inserts 33. Positioned above the planeof motion of block 31 and directly above the center of disk 32 is acircular guide 38. A cord or wire 39 is attached to the upper surface ofblock 31 at a point directly above contact 37, and is brought throughthe guide 38, over a drum 4%, and attached to the latter. An arm 41 isfixed to rotate with the drum 4!) and its outer end carries the slidingcontact 42 of a variable resistor 43, Whose value at any time ismeasured across terminals A, A. Thus, since guide 3.8 is positioned atthe center of disk 32 and represents the position of the ship and sincethe position of contact 37 represents the position of the target, thelength .of the cord 39 unwound ofi drum 4.0 is a measure of the distancebetween ship and target. If, then the variation in the value of resistor43 is made linear with respect to changes in this distance, its value isa measure of range between ship and target.

Fig. 2 illustrates schematically the electrical connections betweencontact 37 on block 31 and the contact inserts 33 on disk 32. Individualleads connecting to the various contact inserts 33 may be brought offdisk 32 by convenient means, such as slip rings, for connection to oneside of terminals B, while the other side is connected to contact 37 onblock 31. Since the configuration of thecontact inserts, asa whole,represents the sound beam pattern, the individual resistors 44,connected in series With the respective inserts, are chosen of a valueto attenuate any signal in an amount corresponding to their position inthe simulated sound'beam. Thus, progressing from the center of the disk32 toward the edge, the inserts are associated with resistors of greaterand greater value, to lessen the intensity of an echo obtained fromcorrespondingly greater and greater ranges. Similarly, progressingoutwardly in either direction from a radial line bisecting thesimulatedsound beam, the valueof corresponding resistors increases tosimulate the off target attenuation. observed in actual practice.

When thepresent invention' is used in conjunction with the electricalcircuit of Fig. .4 in the application Serial No. 535,858, filed 'May 16,1944, this circuit is modified in accordance with the present inventionas illustrated in Figure 5 wherein elements also appearing in Figures 1through 4 are assigned the same reference characters. Other'elementsdisclosed in Figure 4 of the copending application are designated onlygenerally in Figure 5, reference' being had'to the copending applicationfor. circuitidetailsendoperation. r

It sufiices to state herein that the generator 80 operates to develop asimulated echo signal which Continuously supplies a push-pull outputsignal at the tapped secondary winding 81. This signal is applied to thegrids of a pair of balanced modulator tubes 82 and 83 whose gain isafiected by an amplitude control 84 acting as self-bias and governed bythe control grid bias supplied by conductor 85. The plates of thesetubes drive the output circuit including transformer 86 and attenuator87; This output circuit is connected to supply the audio stages of thereceiver 88 of the echo-ranging gear the output of which, in turn, isnormally available in the loudspeaker 89.

The simulated echo is transmitted to the receiver 88 under control ofthe keying circuit which exercises control over modulator tubes 82 and83 to produce echo simulation from an actual target. This isaccomplished by applying a keying pulse by way of conductor 90 which isconnected to the screen grids of tubes 82 and 83. N transmission resultswhen the screen grids are negative with respect to the cathodes of thetubes and occurs when the potential on the screen grids approaches thatlot the plates of the tubes. The strength of the transmission isgoverned by the bias supplied by amplitude control 84 and conductor 85as will become more fully apparent as the description proceeds.

The simulated echo signal must occurat the proper time after theoutgoing signal or ping of the associated echo-ranging equipment, andfurther, must be of proper duration. In the standby condition,multivibrator tube 91 is conducting and multivibrator tube 92 is non-comducting with the result that potential on the plate of tube 91 which isapplied to the screen grids of tubes 82 and 83 by way of conductor 90 iseffective to cut off transmission of the simulated echo signal.

When a ping received from transmitter 93 and relay 94 is transmitted bysound projector 95, a short A. C. pulse which exists only during theperiod of the outgoing ping, operates relay 96. When the relay is thusenergized, its normally open contacts 97 are closed to dischargecondenser 98 and its normally closed contacts 99 are opened toextinguish tube 180. At the end of the ping the relay contacts arerestored to their initial positions whereupon condenser 98 charges byway of tube 101 and potentiometers 43 and 192 and tube 100 fires, thetime being controlled by the resistance values of otentiometers 43 and102 and corresponding to the echo delay time found in sound gearoperation.

The firing of tube 100 supplies a pulse to multivibrator tube 92 andrenders it conducting and it, in turn, extinguishes multivibrator tube91 whereupon the potential on conductor 96 is elevated at the screengrids of the modulator tubes 82 and 83 to cause transmission of thesimulated echo which continues for a period controlled by the RC circuitincluding potentiometer 103 and condenser 104. l

In the Bearing control circuit of Figure 4 of the aforesaid copendingapplication, tube 27 and its plate load resistor constitute a variableresistor which is controlled by the input to the tube and which isreplaced in the instant case by the particular resistance 44 whosecontact 33 is engaged by contact 37. Thus, terminals B, B of Fig. 2 areconnected between the center tap of the secondary output winding 81 andthe +150 volt terminal on the power supply shown in that applicationfSince, as has been stated, the Bearing control section of that circuitis not used, the value ofthe particular resistor 44 connected in thecircuit, determines the voltage applied to the center tap of winding 81and thus determines the attenuation in the Output circuit correspondingto that observed at varying ranges and bearings.

Terminals A, A of the subject application are arranged to connectvariable resistor 43 into the electrical circuit of the above mentionedapplication, in place of variable resistor 40 therein. value has beenshown to be dependent on range) deter- 6 mines the delay time in theKeying circuit between ping" andecho, as described in that application,in connection with resistor 40, therein.

Attenuator 13 shown in that application thus no longer is varied withrange, but may conveniently be used as a gain control and an impedancematching device for the Output circuit.

The invention, as described above, is made more useful by the insertionof a plurality of memory devices 45, 46, 47, 48, 49 on the inputs ofdifierentials 13, 14 and on the ships course input of differentials 35.Their use may be best explained by understanding that in the ordinaryattack upon a submarine, the underwater ordnance has a sinking time ofseveral seconds, during which the target continues to move. Likewise,the ship continues to move, but its motions can no longer have anyeffect upon the incidence of bomb and target. If, then, it is desired totrain crews in this phase of operation, the memory devices Thus, thevalue of resistor 43 '(whose may be used.

Technically, these units might be more accurately termed overtakingdelay mechanisms, as they enable the driven element to be stopped for apre-determined period and yet quickly restored to the position which itwould have occupied had the delay not occurred. For example, as usedhere, means are provided for the student crew to actuate two of thesemechanism 45, 46 at a time at which depth bombs (or other ordnance)would ordinarily be dropped. The actuation of these mechanisms preventsthe difierentials from applying the components of ship motion to theindicating and electrical control mechanisms and only the targets motionis transmitted. In elfect, the simulated ship is stopped for a periodlong enough for the simulated charges to sink, while the motion of theimaginary target continues. If, as can be determined from the indicatingmechanism, the position of the target (as evidenced by the intersectionof the hairlines) is within the lethal range of the charges after thesinking period has elapsed, the instructor may score the simulatedtarget as sunk. Since this scoring operation may take some little time,an additional set of memory or overtaking mechanisms 47, 48, operated bythe instructor, is also included, in order that the targets motion mayalso be stopped during this period.

Since, however, it is desirable to continue the attack procedure,particularly if the tarket is not sunk, the memory or overtakingmechanisms are arranged to be released by the instructor (after scoring)to bring the ship and simulated target to the relative positions whichthey would have occupied had the delay not been introduced. The attackmay then be continued, as though no interruption had occurred.

So that this procedure may be even more accurately simulated, a similarovertaking mechanism 49 is included between the gyro-compass repeater 19and difierential 35, so that during the scoring period, changes in theships course do not affect the indicating mechanism. This unit, likeunits 47, 48 is under the control of the instructor.

One of the memory or overtaking devices illustrated schematically inFig. 1, is shown in detail in Figs. 3 and 4. Each of these mechanisms isidentical and they are used to restore the various elements to theiroriginal positions after the scoring operation has been completed.

In Fig. 3, the mechanism is seen to have a separate input shaft 51 andan output shaft 52 mounted in position by convenient supports 53, 53. Adish-shaped housing 54 is fixedly secured near the end of the inputshaft 51 and a similar housing 55 is fixed to output shaft 52 in such aposition that the open faces of the housings are opposed. Within therespective housings 54, 55 are a pair of pre-loaded, flat, spiralsprings 56, 57, secured to the inner faces of their respective housingsby means of pins 58, 59, respectively. The other and inner end of eachof the springs 56, 57 is secured by means of pins 60, 61 to the oppositeends of a spool 62 positioned around shafts 51, 52. This spool isexternally threaded between its flanges, as at 63, with right-handthreads extending 'over half this distance and left-hand threadsextending over the remaining half.

Two nuts 64, 65 engage the threaded portion of the spool and aremounted, in their static positions, adjacent the flanges on spool 62.These nuts are provided with pins 66, 67, respectively, which arepositioned to engage small offsets 68, 69, respectively, on the innersurfaces of the spool flanges. The pins and offsets overlie one anotherfor a distance approximately equal to the pitch of the threads on spool62 so that after one of the nuts makes one complete revolution withrespect to the spool, its pin no longer engage the associated ofiset onthe spool flange. The housings 54, 55 are also provided with anotherpair of pins 70', 71, respectively, which extend through the outer edgesof the associated nuts 64, 65.

Associated with and as a component part of this mechanism is a magneticbrake mounted on the output side. The brake comprises a coil of wire 72held in position around output shaft 52 by a magnetic housing 73 which,in turn, is secured to support 53 by any convenient means. Adjacent thebrake housing i a magnetic plate 74 loosely secured to the back ofhousing 55 by an extension of pin 71 and an additional pin 75. Thus,when the brake housing 73 is magnetized, plate 74 is attracted to themagnetic brake housing 73 to lock housing 55 and nut 65.

Four operating conditions are to be considered: (1) input shaft rotatingcounterclockwise, brake not actuated; (2) input shaft rotatingclockwise, brake not actuated; (3) input shaft rotatingcounterclockwise, brake actuated; and (4) input shaft rotatingclockwise, brake actuated.

If the input shaft 51 i rotating counterclockwise with the brake notactuated, it will drive housing 54, which in turn drives nut 64 by meansof pin 76. 'Spool 62 is directly driven by the rotation of nut 64through the engagement of pin 66 with offset 68. On the output side,spool 62 drives housing 55 by virtue of the pre-load on spring 57,which, in turn, is secured to output shaft 52. Thus, in this case, theoutput shaft is driven at the same rotational speed as the input shaft.

In case 2, the same function is performed, although now housing 54drives spool 62 through the pre-loaded spring 56. Spool 62, in turn,drives the housing 55 and output shaft 52 by means of the directengagement of ofiset 69 with pin 67.

In case 3, where the brake is actuated and the input shaft is rotatingcounterclockwise, spool 62 is driven in the same manner as in case 1.Since, however, shaft 52, housing 55 and nut 65 are fixed by theoperation of the brake, rotation of spool 62 simply stores energy inspring -57. Since, however, spool 62- is rotating and nut 65 is fixed,the spool threads through the nut 65 (as, after one turn, pin 67 andoffset 69 will not engage) the same number of turns as are made by inputshaft 51. Subsequently, when the brake is released, the energy stored inspring 57 is used to rotate housing 55 and output shaft 52 in the samenumber of turns as Were made by input shaft 51. The rotation of housing55 also restores nut 65, by means of pin 71, to its original positionwith respect to shaft 51.

In case 4, with clockwise rotation of the input shaft, while the brakeis actuated, clockwise rotation of spool 62 is prevented by the offset69 and pin 67. This causes nut 64 to progress along the threads on spool62 (since after one turn, pin 66 and offset 68 no longer engage), and,at the same time, energy is stored in spring 56. When the brake is againreleased, the energy in spring 56 drives the output shaft 52 throughspool 62, offset 69, pin 67, nut 65, pin 71 and housing 55, through thesame number of turns as were made by input shaft 51 while the brake wasactuated.

It should be noted that the action of the memory or overtaking mechanismis limited only by the distance-that nut 64 (or nut 65) may progressalong the threads on spool 62 before the adjacent ends of pins 66, 67engage each other. '-It should further be noted that in Fig. 4, the.spring 57 is schematically illustrated and has, in actual fact, manymore turns than are illustrated.

The electrical operation'of one of the magnetic brakes is illustrated inFig. 3. The coil 72 is energized by current from battery 76, when thecircuit i closed by means of key 77. As described above, one suchcircuit, with the coils in series, may be used by the instructor toactuate overtaking mechanisms 47, 48, 49 and a similar circuit may beused by the student crew to actuate units 45, 46. Conventional relay maybe provided in order that the instructor may release both of the keys atonce at the end of the scoring in order that the driven shafts may berestored to the position they would have occupied had the magneticbrakes not been applied.

In operation, connections are made to the electrical circuit atterminals A, A and B, B, as described above. The associated echo-ranginggear is put into operation and' the speed of motor 2 is set tocorrespond to the ships speed, subsequent and corresponding changes inwhich may be made automatic-ally or manually. The North-South andEast-West components of this motion, whose respective magnitudes aredetermined by the heading of the ship as controlled by the gyro-compassrepeater 10, are obtained from the ball solver 4 and applied todifferentials 13, 14, respectively. The speed and course of thesimulated "target are controlled by the instructor by means of motors 1,9, respectively. Ball solver 3 likewise supplies the north-south andeast-west components of this simulated target'motion to thedifferentials 13, 14. The difference component (or the components ofrelative motion between ship and simulated target) are directly appliedto the driven rollers 15, 18. Operation of the curtains 16, 19 and theintersecting hairlines 17, 20, by means of such rollers, effectivelyportrays the relative motion of the target with respect to the ship(fixed point 22). The instructor has before him the indicating mechanismon the plotting table with the indicating mechanism showing the positionof the simulated target and bearing of the position. The crew beingtrained is not permitted to see this bearing or position indicator, northe electrical control mechanism which is also a part of the plottingtable. The crew is at stations operating the sound gear of the ship, onwhich is signaled the simulated target noise as heretofore described.

Thus, as the ship is conned, the instructor is enabled to observe theprogress of its maneuvers as the student crew attempts to bring it intoa position for the attack on the simulated target. Not only is heenabled to judge the relative positions, but the direction indicated byarrow 23 tells him, at all times, the direction in which the studentsare heading the ship. Additionally, by operating the controls on targetmotors 1, 9, he may cause the simulated target to take evasive ac "on,as might be true in actual practice.

The student crew is, during the simulated attack (in which the shipactually maneuvers), conning the ship on the basis of the audible andvisual information made available at the sound gear. Block 31 (on theelectrical control mechanism) is, as has been described, at the sameposition with respect to the ship (represented by the center of disk 32)as is the simulated target. If the students train the sound projectortoward the target, disk 32 occupies a position (determined by the outputof differential 35) such that the output circuit is closed by means'ofcontact 37 and one of contact inserts 33. An echo signal will thus beintroduced into the echo-ranging gear, a described in the applicationmentioned above. The proper delay between the keying ping and the echo,which is obviously a measure of range, is determined in the keyingcircuit as controlled by the setting of variable resistor 43. Its value,in turn, is dependent upon the angular positionbf drum 40 as a measureof the distance between contact 37 (simulated target) and the center ofdisk 32 (ship).

The variation in echo strength observed with varying ranges is obtained,as has been described, by the different values of resistors 44(associated with insert contacts 33) which attenuate the signal appliedto the output circuit more and more, as the range increases. In :asimilar manner, this signal is attenuated more and more as contact 37moves away from the center line of the configuration of contact inserts33 (corresponding to training of the projector away from the targetsbearing), until the circuit is broken. Obviously no echo is heard duringthe periods in which contact 37 touches only the non-conducting portionsof disk 32, as such positioning indicates that the sound projector isnot being trained in the direction of the target.

In order to illustrate the scoring procedure, assume that the studentcrew has maneuvered the ship to a point at which it considers that depthcharges should be dropped. Instead of actually doing so, the crew willactuate the key 77 which with battery 76 controls the overtakingmechanisms 45, 46. This prevents rotation of the output shafts, and as aconsequence, the only components of motion applied to move hairlines 17,20 and block 31 are those of the simulated target. Thus, the indicatingmechanism, during this period portrays the motion of the target (theintersection of the hair-lines) with respect to the point where thecharges were dropped by the ship (reference point 22). After the sinkingtime has elapsed, the instructor operates another key 79 acting withanother battery 78 to lock the magnetic brakes on overtaking mechanisms47, 48, 49, which operation fixes the simulated target position (theintersection of the hairlines) with respect to the point of explosion ofthe charges (reference point 22) By measuring the distance between thesepoints, the instructor is enabled to determine whether or not the targetwas within the lethal range of the charge, or charges. When scoring iscompleted, the instructor may release all of the magnetic brakes andrestore the hairlines and block 31 to the positions they would haveoccupied had the brakes not been actuated.

In connection with the use of these mechanisms, it is to be noted thatany conventional delay mechanism may be utilized to automaticaliyactuate the target overtaking mechanisms 47, 48, 49 at anypre-determined (sinking) time after the ship mechanisms 45, 46 have beenoperated. It should also be noted that the overtaking mechanisms may bearranged to be effective only on the motions portrayed on the indicatingmechanism, in order that even during sinking and scoring time, theelectrical control mechanism may be affected by continuing motion ofship and target, and, as a conesquence, continues to supply correctsignals to the sound gear. Such an arrangement, however, requires moredifferentials and its advantages are =1argely overcome by the fact thatduring an actual at tack, the sound gear provides very littleinformation for a considerable period after the explosion of depthcharges.

Having described our invention, we claim:

1. In a device for training students in the use of shipboard mountedunderwater sound echo-ranging gear, said gear including a transmitter, areceiver and an underwater sound projector, the combination comprising;a rotatable plotting table having a mark thereon constituting areference point representing the position of said ship, a contactmember, means mounting said contact member for independent motions alongat least two orthogonal coordinates, means for separately applying thecomponents of motion between said ship and a simulated moving target todrive said contact member, a plurality of conductive inserts arranged ina pattern corresponding to the lobe pattern of the underwater pulseemitted from said projector, means mounting said insert pattern forrotation about said point as a center, and means for maintaining saidinsert pattern in a direction corresponding to the ,direction in -whichthe sound projector is} trained whereby contact will be made betweensaid contact member and one of said conductive inserts when said soundprojector is trained in a direction corresponding to" member occupiesrelative the position which said contact to said reference point.

2. In a device -for training board mounted underwater soundecho-ranging'gear, said gear including a transmitter, a receiver and anunderwater sound projector, and in which signal pulses of supersonicfrequency from said transmitter emitted by said projector are echoedback thereto from a target for detection in said receiver, thecombination comprising; means \for generating signal pulsescorresponding to pulses emitted by said projector, circuit means forapplying said generated pulses to said receiver subsequent to pulseemission to simulate a pulse echo from an actual target, and a switchingdevice connected in said circuit means for preventing application ofsaid generated pulses except when said projector is trained in adirection corresponding to the direction of the simulated targetrelative to said ship, said switching device comprising; a rotatableplotting table having a mark thereon constituting a reference pointrepresenting the position of said ship, a first switch contact member,means mounting said contact member for independent motions along atleast two orthogonal coordinates, means for separately applying thecomponents of motion between said ship and the simulated target to drivesaid contact member, a plurality of conductive inserts arranged in apattern corresponding to the lobe pattern of the pulse emitted by saidprojector with each insert constituting a second switch contact member,means mounting said insert pattern for rotation about said point as acenter, and means for maintaining said insert pattern in the directionin which said sound projector is trained whereby contact between saidfirst contact member and one of said second contact members will beestablished only when said sound projector is trained in a directioncorresponding to the position which said first contact member occupiesrelative to said reference point.

3. Apparatus for shipboard training with echo-ranging equipmentcomprising a rotatable table having a point thereon and a line throughsaid point representing respectively the position of a ship and itsheading, means responsive to the heading of said ship for rotating saidtable, a pair of movable transparent curtains positioned over saidtable, said curtains each having a line at right angles to each other,separate means for moving each of said curtains in a path normal to theline on each, said moving means being responsive to components ofrelative motion between the ship and a simulated target whereby saidcurtains and the lines thereon are moved in accordance with saidcomponents.

4. Apparatus for shipboard training with echo-ranging equipmentcomprising a directional signal projector, means generating componentsindicative of ship and simulated target position, a rotatable dischaving a plurality of contacts thereon arranged in a patterncorresponding to the lobe pattern of said projector, means responsive tothe bearing of said projector for rotating said disc, a movable member,means responsive to said components for moving said member, anelectrical circuit including a contact on said member adapted to closesaid circuit through one of said plurality of contacts whenjuxtapositioned therewith, a guide positioned centrally on said disc, arotary potentiometer, and an elongated element connected to said memberand said potentiometer and extending through said guide for adjustingsaid potentiometer in accordance with the position of said member.

5. Apparatus for shipboard training with echo-ranging equipmentcomprising a directional signal projector, means generating componentsindicative of ship and simulated target positions, a rotatable dischaving a plurality of contacts thereon arranged in a patterncorresponding to the lobe pattern of said projector, means responsivestudents in the use of ship-

